1. Field of the Invention
The invention generally relates to a headlamp assembly having low beam and high beam operation modes and a multi-focal condenser lens.
2. Background of the Invention
Many projector headlamp units have two functions—low beam and high beam. Referring to FIG. 1, a prior art headlamp assembly is generally shown at 10. The headlamp assembly 10 includes a light source 12, a reflector surface 14, and a condenser lens 16. Switching between high beam and low beam is done by a movable shield 18. The shield 18 is moveable between a first position, shown in solid lines, and a second position, shown in dashed lines. In the first position, the shield 18 stops the light 20 reflecting from certain portions of the reflector surface 14 so that this light 20 cannot hit and pass through the condenser lens 16. Thus, the shield 18 creates the cutoff line of the low beam. In the second position, the shield 18 is moved out of the way and allows this light 20 reflecting from the reflector surface 14 to come over the shield 18 to the condenser lens 16 to provide a high beam function.
The problem associated with this type of headlamp is the need to achieve an ideal balance between low and high beam according to photometrical regulations. Regulations require that the high beam meet minimal values and the low beam meet maximal values within measurement points laying very closely to one to another.
There are two current solutions to this problem. The first one uses an optical design of the reflector surface to create an extreme gradient between the high beam and low beam regulation points. The second current solution is illustrated in FIG. 2. In FIG. 2, a headlamp assembly 110 includes a light source 112, a reflector surface 114, a condenser lens 116, and a shield 118. The shield 118 includes a first portion 118a and a second portion 118b. The second portion 118b is spaced from the first portion 118a at a distance in front of the first portion 118a. The second portion 118b of the shield 118 decreases the intensity closely below the low beam cutoff, such that the low beam meets the maximal requirements.
These solutions meet the maximal and minimal requirements for low beam and high beam operation, but only by a small margin. Therefore, there is a need for a headlamp assembly that provides an optimal balance between the low beam and high beam operation, such that both the low beam and high beam have good intensity values that meet the maximal and minimal requirements.